The present invention relates generally to an apparatus and method for fabricating stents by deforming patterned sheets into substantially tubular shapes and connecting the edges of the sheet. More specifically, the invention is especially directed to an apparatus and method that is especially applicable to making stents having weld point pairs that are not disposed along a single weld line when the sheet is rolled into a substantially tubular shape.
Stents are known in the art. They are typically formed of a cylindrical metal mesh which can expand when pressure is internally applied. Alternatively, they can be formed of wire formed into a cylindrical shape.
U.S. Pat. No. 5,906,759, which is hereby incorporated herein by reference in its entirety, provides a stent fabrication method which can produce stents with intricate and delicate designs. In particular, the stent fabrication methods and apparatus described at columns 10-26 of that patent (and the accompanying figures) may be advantageously used along with the present invention. The method disclosed in the ""759 patent involves first creating a version, preferably flat, of the desired stent pattern from a piece of thin material, e.g., sheet metal. The flat pattern can be produced through a variety of suitable techniques that are well known to those skilled in the art. Once the flat pattern has been formed, it is deformed so as to cause its edges to meet.
To create a cylindrical stent from a flat metal pattern, the flat metal is rolled or wrapped around a mandrel until the edges meet. The locations where the edges meet are joined together, such as by laser welding. Afterwards, the stent may be finished in a variety of well known ways, e.g., polishing, either mechanically or electrochemically, plating, or applying a medicament or some other coating.
In making stents for specific applications it may be desirable to utilize sheets which, when rolled into a tube, have weld points that are not disposed along a single weld line disposed along the longitudinal axis of the mandrel. Instead, for example, the weld points may be disposed on one or more weld lines that are disposed laterally to the longitudinal axis of the mandrel. If a mandrel having a substantially circular cross-section is used, the greater the distance that the weld points are displaced laterally from the longitudinal axis of the mandrel, the more acute will be the angle that the laser beam makes with the weld points.
Accordingly, it is an object of the invention to remove the drawbacks of the prior art and to provide an apparatus and method which allows for the making of stents utilizing sheets which when rolled into a tubular shape have weld points that are not disposed only along a single weld line, while still allowing the laser beam to intersect the weld points at an angle that is substantially perpendicular.
In accordance with an exemplary embodiment of the present invention, it is an object of this invention to provide a mandrel for forming a stent, comprising: a member having a first end, a second end and an external surface with the external surface provided with at least one substantially flat surface extending between the first end and the second end.
It is another object of this invention to provide a mandrel for forming a stent comprising: a longitudinal member having a first end and second end. The longitudinal member has a substantially triangular cross-sectional shape, wherein each of the three sides defining the substantially triangular shape is a substantially flat surface that extends between the first end and the second end of the mandrel.
It is yet another object of this invention to provide an apparatus comprising a mandrel having an axis, and having a substantially flat surface. A means is provided to wrap a flat sheet provided with a stent pattern around the mandrel so that the edges of the sheet meet on or near the substantially flat surface of the mandrel. A means for joining the edges together may be disposed adjacent to the mandrel to provide, for example, energy such as a laser beam directed at an angle substantially perpendicular to the flat surface. Alternatively or additionally, the means for joining may also provide an adhesive, such as glue. The means for joining may be supported for movements in directions parallel to and orthogonal to the axis of the mandrel to permit joining at points which are laterally displaced from each other on the flat surface.
It is still another object of this invention to provide and apparatus for fabricating a stent, comprising: a platform adapted to receive a sheet of material to be formed into the stent. The sheet has a longitudinal axis, a first major surface, a second major surface, a first long side, and a second long side. The first long side is provided with a plurality of weld points and the second long side is provided with a plurality of corresponding weld points. The weld points are disposed so that when the sheet is formed into a substantially tubular shape, the weld points on the first long side are adjacent to the corresponding weld points on the second long side to form a plurality of weld point pairs. A mandrel having an external surface and a first end and a second end defining a longitudinal axis is provided. The mandrel is sized to have an external perimeter about the longitudinal axis that is substantially equal to or less than the unexpanded internal perimeter of the stent to be fabricated. The external surface of the mandrel is provided with at least one substantially flat surface extending between the first end and the second end. A means is provided for deforming the sheet against the external surface of the mandrel so that the sheet is deformed into a substantially tubular shape. A means for aligning and securing is provided for aligning and securing the weld points on the first long side and the corresponding weld points on the second long side to form a plurality of weld point pairs so that they can be connected, e.g., by welding. A means for joining, for example, a laser, may be provided for joining the weld points on the first long side to the corresponding weld points on the second long side. The means for deforming and the means for aligning and securing are adapted to secure the aligned weld points adjacent to the substantially flat surface of the mandrel so that each of the aligned weld points comprising each of the weld point pairs lies in a plane that is substantially perpendicular to the laser beam.
It is a further object of this invention to provide an apparatus for fabricating a stent, comprising: a platform adapted to receive a sheet of material to be formed into the stent. The sheet of material has a longitudinal axis, a first major surface, a second major surface, a first long side, and a second long side with the first and second long sides substantially parallel to the longitudinal axis of the sheet. The first long side may be provided with a plurality of first weld line weld points and a plurality of second weld line weld points and the second long side may be provided with a plurality of first weld line weld points and a plurality of second weld line weld points. The weld points are disposed so that when the sheet is formed into a substantially tubular shape the first weld line weld points on the first long side are adjacent to the corresponding first weld line weld points on the second long side to form a plurality of first weld line weld point pairs disposed on a first weld line having a longitudinal axis substantially parallel to the longitudinal axis of the sheet. The weld points are also disposed so that when the stent is formed into a substantially tubular shape the second weld line weld points on the first long side are adjacent to the corresponding second weld line weld points on the second long side to form a plurality of second weld line weld points disposed on a second weld line having a longitudinal axis that is substantially parallel to the longitudinal axis of the sheet. Of course, the weld points on the first long side and the second long side need not actually be disposed on lines at all; they need only meet in weld point pairs when the sheet is rolled and the first and second long sides meet each other. A mandrel having an external surface and a first end and a second end defining a longitudinal axis is provided. The mandrel is sized to have an external perimeter about the longitudinal axis that is substantially equal to or less than the internal perimeter of the stent to be fabricated. The external surface of the mandrel is provided with at least one substantially flat surface extending between the first end and the second end. A means is provided for deforming the sheet against the external surface of the mandrel so that the sheet is deformed into a substantially tubular shape. The means for deforming is adapted so that the first long side and the second long side remain substantially parallel to each other when the sheet is deformed into the tubular shape. A means is provided for aligning and securing the weld points on the first long side to the corresponding weld points on the second long side so that the weld points form weld point pairs that can be connected. A means for joining, for example, a laser, may be provided for securing the aligned weld points. The means for deforming and the means for aligning and securing are adapted to secure the aligned weld points adjacent to the substantially flat surface of the mandrel so that the aligned weld points lie in a plane that is substantially parallel to the substantially flat surface of the mandrel and substantially perpendicular to the laser beam.
It is a still further object of this invention to provide a method of making a stent comprising: wrapping a sheet provided with a stent pattern and having two opposed sides about a mandrel having an axis, and having a flat surface, so as to cause the two opposing sides to meet on the flat surface. A means for joining is utilized for joining the two opposing sides at two or more points not disposed along a single line parallel to the longitudinal axis of the mandrel. The means for joining is directed substantially perpendicular to the flat surface.
It is a yet further object of this invention to provide a method of making a stent, comprising the steps of: utilizing a sheet of material to be formed into the stent, the sheet having a longitudinal axis, a first major surface, a second major surface, a first long side, and a second long side. The first long side is provided with a plurality of weld points and the second long side is provided with a plurality of corresponding weld points. The weld points are disposed so that when the stent is formed into a substantially tubular shape, the weld points on the first long side are adjacent to the corresponding weld points on the second long side to form a plurality of weld point pairs that need not be disposed on only a single weld line. The sheet is deformed against the external surface of a mandrel so that the sheet is deformed into a substantially tubular shape. The mandrel has an external surface and a first end and a second end defining a longitudinal axis. The mandrel is sized to have an external perimeter substantially equal to or less than the internal perimeter of the stent to be fabricated. The external surface of the mandrel is provided with at least one substantially flat surface extending between the first end and the second end. Each of the plurality of weld points is aligned and secured adjacent to the substantially flat surface of the mandrel so that the weld points lie in a plane that is substantially parallel to the substantially flat surface of the mandrel, and so that the weld points on the first long side are adjacent to the corresponding weld points on the second long side to form a plurality of weld point pairs. The corresponding weld points may be connected by utilizing a means for joining, e.g., a laser beam, that is directed substantially perpendicular to the plane in which the weld points lie.
It is another object of this invention to provide a method of making a stent, comprising the steps of: utilizing a sheet of material to be formed into the stent, the sheet having a longitudinal axis, a first major surface, a second major surface, a first long side, and a second long side with the first and second long sides substantially parallel to the longitudinal axis of the sheet. The first long side is provided with a plurality of weld points and the second long side is provided with a plurality of weld points. The weld points are disposed so that when the sheet is formed into a substantially tubular shape, the weld points on the first long side are adjacent to the corresponding weld points on the second long side to form a plurality of weld point pairs. The weld points may be disposed so that the weld point pairs are not all disposed on a single line parallel to the mandrel""s longitudinal axis when the sheet is formed into a substantially tubular shape. The sheet is deformed against the external surface of a mandrel so that the sheet is deformed into a substantially tubular shape. The mandrel has an external surface and a first end and a second end defining a longitudinal axis. The mandrel is sized to have an external perimeter that is substantially equal to or less than the internal perimeter of the stent to be fabricated. The external surface of the mandrel is provided with at least one substantially flat surface extending between the first end and the second end. The first and second weld points are aligned and are secured adjacent to the substantially flat surface of the mandrel so that the weld points on the first long side are adjacent to the corresponding weld points on the second long side to form a plurality of weld point pairs that are not all disposed on a single weld line having a longitudinal axis substantially parallel to the longitudinal axis of the mandrel. Each of the weld point pairs lies in a plane that is substantially parallel to the substantially flat surface of the mandrel. The weld point pairs may be connected by utilizing a laser beam directed substantially perpendicular to the plane containing the weld point pairs.